1. PHP REQUIREMENT LINK : https://docs.clientexec.com/en/article/system-requirements-yl750s/ (7.4 min requirement is mentioned in 6.7.0 changelog)
2. 6.2.x does not work with MySQL 8.0. It will be supported after 6.3.x release. Enable it once 6.3 is released. 
3. Keep the "Default Payment Type Attributes" value as it is in setting table.
4. Keep the default entries in tld_extra_attributes table as it contains generalised data. Check with base64_decode('value');